1. Field of the Invention
The present invention relates to a ratchet wrench and, more particularly, to a oneway ratchet wrench for operating a workpiece, such as a screw, nut and the like.
2. Description of the Related Art
A conventional ratchet wrench in accordance with the prior art shown in FIGS. 6-9 comprises a wrench body 10 having an end portion 17 provided with a mounting hole 11 and a receiving chamber 15 connected to the mounting hole 11, a ratchet wheel 40 mounted in the mounting hole 11 of the wrench body 10 and having an outer wall provided with a plurality of ratchet teeth 41, a pawl member 20 pivotally mounted in the receiving chamber 15 of the wrench body 10 by a pivot pin 30 and having a first side provided with a plurality of locking teeth 21 engaged with the ratchet teeth 41 of the ratchet wheel 40, an elastic member 23 mounted in the receiving chamber 15 of the wrench body 10 and biased between a peripheral wall of the receiving chamber 15 of the wrench body 10 and a second side of the pawl member 20 to push the pawl member 20 toward the ratchet wheel 40, a retaining ring 800 mounted in the mounting hole 11 of the wrench body 10 and abutting the ratchet wheel 40 to retain the ratchet wheel 40 in the mounting hole 11 of the wrench body 10, and a substantially C-shaped snapping member 900 mounted in the mounting hole 11 of the wrench body 10 and snapped onto the retaining ring 800 to retain the retaining ring 800 in the mounting hole 11 of the wrench body 10.
The wrench body 10 is provided with a positioning hole 16 connected to the receiving chamber 15 to allow passage of the pivot pin 30. The end portion 17 of the wrench body 10 has an inner wall having a first side provided with a receiving groove 13 and a retaining groove 14 each connected to the mounting hole 11 and a second side provided with a limit rib 12. The pawl member 20 is provided with a pivot hole 22 connected to the positioning hole 16 of the wrench body 10 to allow passage of the pivot pin 30. The ratchet wheel 40 has an inner wall provided with a driving hole 42 to drive a workpiece, such as a screw, nut and the like. The ratchet wheel 40 has a first side provided with a limit groove 73 facing the receiving groove 13 of the wrench body 10 and a second side provided with a limit recess 44 abutting the limit rib 12 of the wrench body 10. The retaining ring 800 is mounted on the ratchet wheel 40 and has an inner wall abutting the limit groove 43 of the ratchet wheel 40 and an outer wall abutting the receiving groove 13 of the wrench body 10. The outer wall of the retaining ring 800 is provided with a locking groove 810 facing the retaining groove 14 of the wrench body 10. Thus, the ratchet wheel 40 is limited by the retaining ring 800 and the limit rib 12 of the wrench body 10. The snapping member 900 is snapped into the retaining groove 14 of the wrench body 10 and the locking groove 810 of the retaining ring 800 to retain the retaining ring 800 in the wrench body 10.
In operation, referring to FIG. 8 with reference to FIGS. 6 and 7, the driving hole 42 of the ratchet wheel 40 is mounted on a workpiece (not shown), such as a screw, nut and the like. In such a manner, when the end portion 17 of the wrench body 10 is rotated in the clockwise direction, the pawl member 20 is driven by the wrench body 10 to drive the ratchet wheel 40 in the clockwise direction. At this time, the ratchet wheel 40 applies a reaction force on the pawl member 20 in the counterclockwise direction to drive the locking teeth 21 of the pawl member 20 toward the ratchet teeth 41 of the ratchet wheel 40, while the elastic member 23 pushes the locking teeth 21 of the pawl member 20 toward the ratchet teeth 41 of the ratchet wheel 40, so that the locking teeth 21 at one end of the pawl member 20 are engaged with the ratchet teeth 41 of the ratchet wheel 40 closely, and the locking teeth 21 at the other one end of the pawl member 20 are spaced from the ratchet teeth 41 of the ratchet wheel 40 by pivot action of the pawl member 20 about the pivot pin 30. In such a manner, the pawl member 20 is combined with the ratchet wheel 40. Thus, when the end portion 17 of the wrench body 10 is rotated in the clockwise direction, the pawl member 20 is driven by the wrench body 10 to drive the ratchet wheel 40 in the clockwise direction as shown in FIG. 8 so as to rotate the workpiece in the clockwise direction.
On the contrary, referring to FIG. 9 with reference to FIGS. 6 and 7, when the end portion 17 of the wrench body 10 is rotated in the counterclockwise direction, the pawl member 20 is driven by the wrench body 10 to drive the ratchet wheel 40 in the counterclockwise direction. At this time, the ratchet wheel 40 applies a reaction force on the pawl member 20 in the clockwise direction to push the locking teeth 21 of the pawl member 20 to space from the ratchet teeth 41 of the ratchet wheel 40, while the elastic member 23 is compressed by the pawl member 20, so that the locking teeth 21 of the pawl member 20 are disengaged from the ratchet teeth 41 of the ratchet wheel 40, and the pawl member 20 is released from the ratchet wheel 40 as shown in FIG. 9. Thus, when the end portion 17 of the wrench body 10 is rotated in the counterclockwise direction to drive the pawl member 20 in the counterclockwise direction, the ratchet wheel 40 is released from and not driven by the pawl member 20, so that the wrench body 10 performs an idling rotation in the counterclockwise direction.
However, the locking teeth 21 at one end of the pawl member 20 are engaged with the ratchet teeth 41 of the ratchet wheel 40, and the locking teeth 21 at the other one end of the pawl member 20 are spaced from the ratchet teeth 41 of the ratchet wheel 40 by pivot action of the pawl member 20 about the pivot pin 30, so that the locking teeth 21 at one end of the pawl member 20 are easily worn out or broken during a long-term utilization, thereby decreasing the lifetime of the pawl member 20 and the ratchet wrench. In addition, the force applied on the pawl member 20 is concentrated on the pivot pin 30 to produce a stress concentration, so that the pivot pin 30 easily worn out or broken during a long-term utilization, thereby decreasing the lifetime of the pivot pin 30 and the ratchet wrench.